Certain embodiments of the present invention are directed to integrated circuits. More particularly, some embodiments of the invention provide switching controllers and methods for loads. Merely by way of example, some embodiments of the invention have been applied to power transistors. But it would be recognized that the invention has a much broader range of applicability.
Power transistors have been widely used in various electronics systems. In these systems, there often are requirements on voltage ramping slopes and maximum output currents during start-up processes of the power transistors. If the start-up processes are too fast, the output currents during the start-up processes may become so large that loads of the electronics systems can be impacted or even damaged due to low on-resistance of the power transistors.
FIG. 1 is a simplified diagram showing a conventional system including discrete components for controlling ramping slope of output voltage. The system 100 includes a power MOSFET 110, a transistor 120, resistors 130, 132, 134 and 136, capacitors 140 and 142, a resistive load 150, and a capacitive load 160. The system 100 relies on the Miller plateau of the power MOSFET 110 to control the ramping slope of the output voltage.
The magnitudes of the resistors 130, 132, 134 and 136 and the capacitors 140 and 142 often need to be adjusted based on device parameters of the power MOSFET 110. As shown in FIG. 1, the system 100 uses a relatively large number of resistors and capacitors. Furthermore, the system 100 usually cannot effectively protect various components of the system or prevent fire damage to these components in response to short circuits of the loads during the start-up process of the system 100.
Hence it is highly desirable to improve the techniques related to power transistors.